Keyspace events demo integration test

[a-TODO-rov]

Make sure that:

• [ ] You have read the contribution guidelines.
• [ ] You have created a feature request first to discuss your contribution intent. Please reference the feature request ticket number in the pull request.
• [ ] You applied code formatting rules using the mvn formatter:format target. Don’t submit any formatting related changes.
• [ ] You submit test cases (unit or integration tests) that back your changes.